Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Discrete semiconductor devices generally contain one type of electrical component, e.g., light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, and power metal oxide semiconductor field effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, microprocessors, charged-coupled devices (CCDs), solar cells, and digital micro-mirror devices (DMDs).
Semiconductor devices perform a wide range of functions such as signal processing, high-speed calculations, transmitting and receiving electromagnetic signals, controlling electronic devices, transforming sunlight to electricity, and creating visual projections for television displays. Semiconductor devices are found in the fields of entertainment, communications, power conversion, networks, computers, and consumer products. Semiconductor devices are also found in military applications, aviation, automotive, industrial controllers, and office equipment.
Semiconductor devices exploit the electrical properties of semiconductor materials. The atomic structure of semiconductor material allows its electrical conductivity to be manipulated by the application of an electric field or base current or through the process of doping. Doping introduces impurities into the semiconductor material to manipulate and control the conductivity of the semiconductor device.
A semiconductor device contains active and passive electrical structures. Active structures, including bipolar and field effect transistors, control the flow of electrical current. By varying levels of doping and application of an electric field or base current, the transistor either promotes or restricts the flow of electrical current. Passive structures, including resistors, capacitors, and inductors, create a relationship between voltage and current necessary to perform a variety of electrical functions. The passive and active structures are electrically connected to form circuits, which enable the semiconductor device to perform high-speed calculations and other useful functions.
Semiconductor devices are generally manufactured using two complex manufacturing processes, i.e., front-end manufacturing, and back-end manufacturing, each involving potentially hundreds of steps. Front-end manufacturing involves the formation of a plurality of die on the surface of a semiconductor wafer. Each semiconductor die is typically identical and contains circuits formed by electrically connecting active and passive components. Back-end manufacturing involves singulating individual semiconductor die from the finished wafer and packaging the die to provide structural support and environmental isolation. The term “semiconductor die” as used herein refers to both the singular and plural form of the words, and accordingly can refer to both a single semiconductor device and multiple semiconductor devices.
One goal of semiconductor manufacturing is to produce smaller semiconductor devices. Smaller devices typically consume less power, have higher performance, and can be produced more efficiently. In addition, smaller semiconductor devices have a smaller footprint, which is desirable for smaller end products. A smaller semiconductor die size can be achieved by improvements in the front-end process resulting in semiconductor die with smaller, higher density active and passive components. Back-end processes may result in semiconductor device packages with a smaller footprint by improvements in electrical interconnection and packaging materials.
A conventional flipchip type semiconductor die 10 is shown in FIG. 1 with bumps 12 formed on contact pads 14 over active surface 16. Contact pads 14 are laid out in a given pattern having a density and pitch as determined by the input/output (I/O) requirements of the active and passive components in semiconductor die 10. The size of semiconductor die 10 is determined by the electrical functionality of the die and the I/O required for interconnect to the active and passive components of the die. In order to reduce die size and maximize the number of die per wafer, contact pads 14 are typically laid out according to the minimum pitch achievable for the manufacturing process. That is, contact pads 14 are placed as close together as allowed by the manufacturing process to achieve the highest I/O density and minimum possible pitch. In one embodiment, contact pads 14 have a pitch of 80 μm. By using the minimum pitch achievable for the manufacturing process for contact pads 14, semiconductor die 10 can meet the I/O requirements of the active and passive components of the die while minimizing the die size. In one embodiment, semiconductor die is 5.2×5.2 millimeter square (mm2).
Semiconductor die 10 is mounted to substrate 20 with bumps 12 metallurgically and electrically connected to conductive layer 22 formed on the substrate. Conductive layer 22 includes contact pads and trace lines for electrical interconnect through substrate 20. Conductive layer 22 on substrate 20 must be laid out with the same minimum pitch achievable for the manufacturing process, e.g., 80 μm, as used for contact pads 14. That is, the layout of conductive layer 22 has the same I/O density as contact pads 14. The high I/O density layout requirements for substrate 20 substantially increase the cost of the substrate and reduce flexibility in placing conductive layer 22.
In many applications, a plurality of discrete electrical components 24 is mounted to substrate 20. The discrete electrical components 24 require a minimum spacing from semiconductor die 10 to reduce adverse parasitic effects. Accordingly, discrete electrical components 24 are placed a minimum distance D from semiconductor die 10 on substrate 20 to avoid parasitic interference. The minimum spacing D between the discrete electrical components 24 and semiconductor die 10 consumes area on substrate 20 and complicates the routing of trace lines 22.